Inspired by Pluto and her 5 moons, one of which, Charon, is about half as big as Pluto. Pluto and Charon orbit each other every 6 days or so, and they are gravitationally locked, so that each keeps the same face towards the other. Jonathan Coulton wrote a love song from Charon to Pluto, which is one of the best love songs ever. {soppy on] I sing it to my daughter. [soppy off]